1. Field of the Invention
The present invention relates to a reversible device for the fixation of an implant in the bone of a patient.
2. Brief Description of the Related Art
U.S. Pat. No. 5,501,695 discloses a device for the fixation of a suture anchor in the bone, which device consists of two separate parts.
The fixation device comprises a first firmly attached external, cylindrical element affixed to fixation prongs that are separated from each other by grooves running parallel to the longitudinal axis of said device. The first element accommodates on its inside a second element of deformation that interacts with the free extremity of the fixation prongs.
The second element of irreversible deformation is firmly affixed through a fracture zone to a tie rod which enables the surgeons, after having inserted the suture anchor into a hole previously drilled in the bone, to have the second element slide inside of the first one to axially deform the fixation prongs in the area of the spongy bone.
Since the tractile force is sufficient to deform the fixation prongs, the rod separates from the second element by an irreversible break.
It can be noted that the prongs deform laterally following a direction essentially perpendicular to the longitudinal axis of the suture anchor in order to permanently fasten the latter inside of the bone.
Lastly, to the first element is firmly affixed at one its extremities a flange that comes to rest against the cortical bone and into which are drilled a number of holes for the fastening of the suture threads by the surgeon.
The above-described fixation device presents some disadvantages, namely, that it does not allow the removal of the suture anchor from the bone without causing a complete destruction of the bone and of the bone to which it is attached. In fact, the suture anchor is not provided with any means of removal that would allow it to be disengaged from the bone without causing any damage to it.
Moreover, beyond the fracture zone of the second element, the fixation device is not provided with means that limit the displacement of said element to prevent the fixation prongs from breaking in an abnormal manner under the effects of the tractile force.
Also, U.S. Pat. No. 5,472,452 discloses a fixation device for a suture anchor provided with expansion means that are plastically deformed by means of an appliance.
This fixation device is provided with expansion means that are reversible within the direction of the stress of the appliance and, in particular, of the structure of the implement whose thruster presents an inclined plane allowing the means of expansion to descend into the body of the suture anchor in order to be able to remove it.
This fixation device relates to a suture anchor that is not provided with means to delimit the plastic deformation of the expansion means when a tractile force is applied, in order to prevent an abnormal rupture or an excessive plastic deformation which would render the fixation device irreversible.
Also known are other anchor fixation devices, either by force or by screws, that do not allow a removal of the implant without causing damage to the bone.
The present invention has the aim to specifically remedy these disadvantages.
The fixation device in accordance with the present invention has as object that of being reversible, thus allowing its removal from the bone without having to drill a hole of greater diameter than that of the deformed prongs.
The fixation device in accordance with the present invention is provided with expansion means that are reversible in the direction of the force in order to allow either the fixation of the implant to the bone or its removal.
The fixation device in accordance with the present invention comprises expansion means whose plastic deformation is limited by stop means when a force is applied for the fixation of the implant to the bone, so that said expansion means become reversible when another force is applied enabling the removal of the implant from the bone.
The fixation device in accordance with the present invention comprises expansion means that are limited by stop means in their plastic deformation when a force is applied that allows the fixation of the implant to the bone, so that these expansion means be reversible when another force is applied that allows the removal of said implant from the bone.
The fixation device in accordance with the present invention is provided with expansion means that consist, on the one hand, of a cylindrical section provided with an internal threaded borehole, at least two fixation prongs arranged parallel to the longitudinal axis and on the extension of the cylindrical section, and at least two stops inserted between each prong that limit the plastic deformation of said prongs, and a conical point with a threaded blind hole on its inside.
The fixation device in accordance with the invention is provided at the level of its conical point with a threaded blind hole intended for a threaded rod of an attachment to deform the fixation prongs subjected to a tractile force in a direction essentially parallel to the longitudinal axis.
The fixation device in accordance with the present invention is provided in its cylindrical section with a threaded borehole that is intended for a threaded hollow rod of another attachment, while another rod sliding inside the first one comes to rest against the bottom of the threaded blind hole to open, under the effect of a thrust force, the fixation prongs in a position essentially identical to the original one in order to be able to remove the implant from the bone.
The below description, taking into account the accompanying drawings, given as not limiting examples, allows a better understanding of the invention, of its characteristics and the advantages it may provide.